Results

We identified 11870 records. The PRISMA flow diagram is presented in Figuare 1. A total of 11 studies with data from 771 participants were eligible for inclusion.The additional texts included secondary analyses, abstracts, trial registries, and protocol papers.

Figure 1: PRISMA flow diagram

Study description

10 of the studies were RCTs, and 1 was a crossover RCT (Greene & Petruzzello, 2022).The specific intervention and comparison groups for the 11 eligible studies (13 comparisons) are presented in Table 1.

Study Intervention Comparison Exercise type Therapy TAU Attention control
Bryant2023 exercise + therapy attention control + therapy aerobic exposure therapy NA static stretching
Voorendonk2023 exercise + therapy attention control + therapy mixed PE + EMDR NA guided (creative) tasks
Nordbrandt2020 exercise + TAU TAU mixed NA combination: medical doctor, 1 to 2 sessions with social worker / psychologist NA
Rosenbaum2014 exercise + TAU TAU mixed NA combination: individual and group psychotherapy, pharmacotherapy NA
Young-McCaughan2022b exercise + therapy therapy only aerobic imaginal exposure NA NA
Huseth2022 exercise only WLC aerobic NA NA NA
Young-McCaughan2022a exercise only TAU aerobic NA self-care intervention delivering educational and instructional information NA
Whitworth2019a exercise only attention control anaerobic NA NA videos on various educational topics (excluding exercise and mental health).
Whitworth2019b exercise only attention control anaerobic NA NA videos on various educational topics (excluding exercise and mental health).
Crombie2021 exercise + extinction learning attention control + extinction learning aerobic extinction learning NA NA
Greene2022a exercise only attention control mixed NA NA remained sedentary in the lab
Greene2022b exercise only attention control aerobic NA NA remained sedentary in the lab
Powers2015 exercise + therapy therapy alone aerobic prolonged exposure NA NA

Aerobic = physical performance behaviour pattern that increases heart rate and respiration while using large muscle groups repetitively and rhythmically; anaerobic = physical performance behaviour pattern that is performed in short intense bursts with limited oxygen intake; mixed = combination of aerobic and anaerobic exercise. TAU = treatment as usual; WLC = waiting list control.

Table 1: Specific interventions for all the included studies

8 of the 11 studies were included in the meta-analyses (Bryant et al., 2023; Huseth, 2021; Nordbrandt et al., 2020; Rosenbaum et al., 2015; Voorendonk et al., 2023; Whitworth et al., 2019a; Whitworth et al., 2019b; Young-McCaughan et al., 2022). Meta-analysis was not feasible for 3 of the 11 studies (Crombie et al., 2021a; Greene & Petruzzello, 2022; Powers et al., 2015). Three of the studies provided follow-up PTSD outcome data which were insufficient for synthesis, which were synthesized descriptively without meta-analysis (Crombie et al., 2021a; Greene & Petruzzello, 2022; Powers et al., 2015). Three studies examined putative mediators which was not sufficient to carry out a meta-analysis (Crombie et al., 2021a; Powers et al., 2015; Whitworth et al., 2019a).

Study characteristics of the 8 studies included in the meta-analysis are are presented in Table 2. From these 8 studies, there were 9 eligible comparisons. One study presented findings from two independent comparisons, including a total of four distinct intervention groups (Young-McCaughan et al., 2022). One of the first authors published findings from two different but methodologically similar trials in the same year (Whitworth et al., 2019a; Whitworth et al., 2019b).

Study Year N Intervention Comparison PTSD tool Trial registered Exercise type Exercise intensity Intervention length FU1 FU2 Country
Bryant2023 2023 130 exercise + therapy attention control + therapy CAPS-IV yes aerobic high 10 weeks 34 weeks NA Australia
Voorendonk2023 2023 120 exercise + therapy attention control + therapy PCL-5 yes mixed moderate 12 weeks 26 weeks NA Netherland
Nordbrandt2020 2020 224 exercise + TAU TAU HTQ yes mixed moderate 20 weeks NA NA Denmark
Rosenbaum2014 2014 81 exercise + TAU TAU PCL-4 yes mixed high 12 weeks NA NA Australia
Young-McCaughan2022b 2022 36 exercise + therapy therapy only PCL-5 no aerobic high 8 weeks 12 weeks 32 weeks USA
Huseth2022 2022 21 exercise only WLC PCL-5 no aerobic moderate 8 weeks NA NA USA
Young-McCaughan2022a 2022 36 exercise only TAU PCL-5 no aerobic high 8 weeks 12 weeks 32 weeks USA
Whitworth2019a 2018 30 exercise only attention control PDS-5 no anerobic high 3 weeks NA NA USA
Whitworth2019b 2019 22 exercise only attention control PDS-5 no anerobic high 3 weeks NA NA USA

TAU = treatment as usual; WLC = waiting list control; CAPS-IV = Clinician-Administered PTSD Scale - 4th edition; PCL-4 = PTSD Checklist - version 4; PCL-5 = PTSD Checklist - version 5; PDS-5 = Posttraumatic Diagnostic Scale – version 5; HTQ = Harvard Trauma Questionnaire; Aerobic exercise = physical performance behaviour pattern that increases heart rate and respiration while using large muscle groups repetitively and rhythmically; anaerobic exercise = physical performance behaviour pattern that is performed in short intense bursts with limited oxygen intake; mixed exercise = combination of aerobic and anaerobic exercise; USA = United States of America.

Table 2: Study characteristics of the 8 studies included in the meta-analysis.

Study characteristics of the 3 studies not included in the meta-analysis are are presented (Extended data). From these 3 studies, there were 4 eligible comparisons. One study reported two comparisons (Greene & Petruzzello, 2022).

Study Year N Intervention Comparison Trial registered Exercise type Exercise intensity Intervention length Country
Crombie2021 2021 38 exercise + extinction learning attention control + extinction learning yes aerobic moderate 3 days USA
Greene2022a 2022 24 exercise only attention control no anaerobic high 130 min USA
Greene2022b 2022 NA exercise only attention control no aerobic  moderate 130 min USA
Powers2015 2015 9 exercise + therapy therapy alone yes aerobic moderate 12 weeks USA

Aerobic exercise = physical performance behaviour pattern that increases heart rate and respiration while using large muscle groups repetitively and rhythmically; anaerobic exercise = physical performance behaviour pattern that is performed in short intense bursts with limited oxygen intake; USA = United States of America.

Table 3: Study characteristics of the 3 studies not included in the meta-analysis.

Primary outcome

PTSD Symptom Severity

Risk of bias for the PTSD symptom severity

The results of the risk of bias assessment per domain and study for the primary outcome, PTSD symptom severity is presented below in Figure 2 of the Extended Data. Nine studies reported PTSD outcome data post-intervention. Two studies did not report PTSD outcome data (Crombie et al., 2021a; Greene & Petruzzello, 2022). Five of the nine studies had an overall high risk of bias, three had some concerns, and only one was had low risk of bias. High risk of bias was mainly due to deviations from intended intervention (D2)(Voorendonk et al., 2023; Whitworth et al., 2019a; Whitworth et al., 2019b), missing outcome data (D3)(Rosenbaum et al., 2015; Voorendonk et al., 2023; Whitworth et al., 2019a; Whitworth et al., 2019b), and selection of reported results (D5)(Voorendonk et al., 2023; Young-McCaughan et al., 2022).

Figure 2 Results of the risk of bias assessment per domain and overall for the PTSD severity outcome

Post-intervention (weeks)

For the studies included in the meta-analyses, the earliest study was performed in 2014, while the most recent study was performed in 2023. The median sample size across the studies was 36 participants per study. The median of the mean participant age was 37 years (ranging from 29 to 50 years). Intervention length ranged from 3 weeks to 20 weeks, with a median of 8 weeks.

8 studies provided data for PTSD symptom severity and contributed 9 effect measures to the PTSD symptom severity meta-analysis. The forest plot for PTSD symptom severity is presented in Figure 3.

Figure 3: Meta-analysis of the effects of exercise on PTSD symptom severity.

The meta-analysis found no evidence of a difference in PTSD symptom severity reduction between exercise and comparison groups (SMD = -0.08, 95% CI -0.24 to 0.07). No statistical heterogeneity was observed (τ2=0).

Subgroup Analyses and Meta-regressions

Subgroup analysis by exercise intensity

The test for interaction found some evidence of a difference between studies with moderate intensity and those with high-intensity exercise (Figure 4). We found some evidence that the effect of exercise might be larger in studies of high-intensity exercise compared to studies with moderate intensity

Figure 4: Sub-group analysis of the effects of exercise on PTSD symptom severity by exercise intensity

Subgroup analysis by specific exercise type

We did not find any important differences between the effects of aerobic, anaerobic, or mixed exercise groups (Figure 5).

Figure 5: Sub-group analysis of the effects of exercise on PTSD symptom severity by specific exercise type

Subgroup analysis by exercise alone or tau/therapy augmented by exercise.

TWe found that studies with exercise alone as intervention were associated with larger effects than those in studies where patients were additionally given treatment-as-usual or psychotherapy (Figure 6).

Figure 6: Sub-group analysis of the effects of exercise on PTSD symptom severity by exercise alone or TAU/therapy augmented by exercise

Meta-regression by intervention length

We performed a meta-regression for the intervention duration, despite the fact that we had only 9 studies (Figure 7). The meta-regression analysis yielded a coefficient of 0.02 (95% CI: -0.01, 0.05), indicating that for every additional week, the standardized mean difference (SMD) in PTSD symptoms increased by 0.02. This suggests there was no meaningful association between intervention duration and PTSD symptom severity

Figure 7: Meta-regression of the effects of exercise on PTSD symptom severity by intervention length

Heterogeneity explained by covariates
Moderator Category \(\beta\) 95% CI 𝞽2
Overall effect - -0.08 -0.24 to 0.07 0
Exercise intensity - - - -
Moderate 0.04 -0.17 to 0.25 0
High -0.23 -0.45 to 0 0
Exercise type - - - -
Aerobic -0.16 -0.43 to 0.1 0
Anaerobic -0.52 -1.13 to 0.1 0
Mixed 0.01 -0.19 to 0.21 0
Exercise augmentation - - - -
Exercise alone -0.38 -0.77 to 0.02 0
TAU/therapy + augmented -0.03 -0.2 to 0.14 0
Intervention length per unit (Week) increase 0.02 -0.01 to 0.05 0

Sensitivity Analyses

We examined the robustness of the findings for the primary outcome by excluding studies with high risk of bias (Figure 8). 3 studies included in the meta-analyses were rated as low or some concerns. WWhen restricting the analysis to the three studies with low risk of bias or some concerns, the effect of exercise on PTSD symptoms severity decreased only slightly SMD = -0.06 (95% CI: -0.27 , 0.14). For reference, the main effect size for the primary outcome was SMD = -0.08 (95% CI: -0.24 , 0.07), so the results do not change substantially.

Figure 8: Meta-analysis of the effects of exercise on PTSD symptom severity when excluding studies with high risk of bias

Reporting bias

Visual inspection of the funnel plot of standard error Hedges’ g suggested possible publication bias in favour the of exercise group.

There was insufficient studies to test for small study effect. The forest plot below shows the meta-analysis results of the primary outcome, PTSD symptom severity, ordered by the precision of the studies is presented in Figure 9. The smaller studies showed larger effects favoring the exercise groups compared to the larger studies which cluster around the line of no effect.

Figure 9: Forest plot of the meta-analysis results of the primary outcome ordered by the precision of the studies


Secondary outcomes

Treatment Dropout

Post-intervention (weeks)

8 studies provided data for treatment dropout, and contributed 9 effect measures to the treatment dropout meta-analysis. The forest plot for the risk of treatment dropout presented in Figure 10.

Figure 10: Meta-analysis of the dropout rates between the intervention and control groups

No evidence of a difference in treatment dropout between exercise and comparison groups (RR = 1.28, 95% CI 0.67 to 2.45) was found and there was large heterogeneity, as shown by the prediction interval (0.16 to 10.15).

Functional impairment

Two studies examined the effects of exercise on functional impairment post-intervention (Nordbrandt et al., 2020; Voorendonk et al., 2023). Nordbrandt et al., 2020 compared treatment as usual (TAU) which constituted of psychotherapy in the form of CBT and acceptance and commitment therapy (n = 104) – with TAU with basic body awareness therapy (n = 105), and exercise plus TAU (n = 109). They did not find any evidence that exercise +TAU is more effective than either TAU or TAU +basic body awareness therapy. Voorendonk et al. compared an 8-day intensive trauma-focused therapy (TFT) programme with (n = 59) and without exercise (n = 60). The intensive TFT programme consisted of daily prolonged exposure, EMDR therapy and psychoeducation complemented with physical activities for the exercise group and controlled mixtures of creative tasks for the control group. They did not find any evidence that exercise is more effective than the control in improving quality of life (Voorendonk et al., 2023).

PTSD symptom clusters

Two of the 11 studies examined the effects of exercise on PTSD symptom clusters, namely avoidance, re-experiencing, hyperarousal, as well as negative cognitions and mood (Whitworth et al., 2019a; Whitworth et al., 2019b). One study reported significantly lower levels of avoidance symptoms (Cohens’ d = 1.26; 95% CI [0.39, 2.14]) and hyperarousal symptoms (d = 0.90; 95% CI [0.06, 1.74]) in the exercise group (n = 15) relative to the control group (n = 15) post-intervention (Whitworth et al., 2019a).While intrusion (d = 0.67; 95% CI [−0.15, 1.49]) and mood and cognitive symptoms (d = 0.34; 95% CI [−0.47, 1.14],) did not differ between the exercise group (n = 15) and the control group (n = 15) post-intervention (Whitworth et al., 2019a). The other study found no significant between-group differences (p>0.05) between the exercise (n = 9) and comparison (n = 10) groups for intrusion (d= -0.65 vs d = -1.25), avoidance (d = -0.95 vs d = -0.92) mood and cognitive symptoms (d= -0.73 vs d = -0.70) , and hyperarousal symptoms (d= -0.43 vs d = -0.59)(Whitworth et al., 2019b).

Loss of PTSD diagnosis

Only one study reported data on loss of PTSD diagnosis post-intervention (Voorendonk et al., 2023). Loss of diagnosis was high in both the exercise and comparison groups. Findings based on the CAPS-5 showed that the loss of PTSD diagnosis post-intervention did not differ between the exercise and the control groups (80.0% versus 82.7%); X2[1] = 0.13, p = 0.72).


SUMMARY OF THE EVIDENCE

The primary outcome was efficacy in reducing overall PTSD symptom severity in patients with PTSD. The summary of the evidence on PTSD symptom severity outcome for PTSD is reported below.

Outcome Summary of the association Within-study biases Across-studies biases Indirectness Other Bias
PTSD symptom severity

Studies = 8 (9 comparisons), Participants = 700; Random effects: SMD = -0.08, 95%CI: -0.24, 0.07 Low to no statistical heterogeneity.

We found some evidence that the effect of exercise might be larger in studies of high-intensity exercise compared to studies with moderate intensity; and that studies with exercise alone as intervention were associated with larger effects than those in studies where patients were additionally given treatment-as-usual or psychotherapy.

We did not find evidence of differences between the effects of aerobic, anaerobic, or mixed exercise groups; or that intervention duration (in weeks) was related to post-intervention PTSD symptom severity.

High risk

Overall, 5 studies had high risk of bias, for 3 studies we had some concerns, and 1 had a low risk of bias.

Bias was mainly due to deviations from the intended intervention, missing outcome data, and selection of reported results. We expect that the bias exaggerates the effect of the intervention.

High risk

It appears that the smaller studies showed larger effects favouring the intervention. Possibly the effect of exercise is exaggerated.

Small number of studies per subgroup

Data from only 9 studies. Additionally, studies may change these findings

Some concerns

Participants Some concerns (no data for child and adolescence. Only adults

Intervention: Some concern (evidence of a larger effect for high-intensity compared to moderate-intensity exercise)

Control: Some concern (some evidence of a difference between exercise alone compared with those with exercise in addition to psychotherapy or TAU)

Outcome: Low risk (Validated PTSD symptom severity measurement scales)

Some concerns

Three studies not included in the meta-analysis due to insufficient data

.